1. Field of the Invention
The present invention is directed to a valve having a transversely movable disc to open and close a fluid conduit and more particularly to a valve having a valve disc with an inflatable tube about the periphery thereof to provide positive sealing engagement of the valve disc within an operating chamber in both the operative and inoperative positions.
2. Prior Art
Typical prior art vacuum valves are gate valves with metal to metal sealing or metal to elastomer sealing. These prior art valves, however, will not be sufficiently leak proof and cannot withstand high temperatures. A disadvantage of the metal to metal sealing valve is the problem of wear after short periods of recycling. A relatively soft metal is needed to prevent leakage but such soft metals are more prone to wear. Elaborate mechanisms have been devised to slide the gate valve into position without scuffing and then locking the gate valve into a closed or open position. Frequent shut down for the replacement of the sealing material was necessary. Some gate valves of aluminum are restricted by outgassing problems. Those using elastomer O-ring seals have the same disadvantage as metal sealing valves in that a cam device or some means of reducing the friction of the sliding parts is needed when moving the gate valve and then pushing it against a seat when closed. In addition, the valve of this type is generally limited to temperatures of 200.degree.C. All the present valves require a means for sealing the actuator shaft. The typical bellows-seal requires frequent replacement.
Other prior arts gate valves utilize some type of inflatable means on the valve disc which may be selectively expanded in the closed position of the valve to provide a sealing arrangement. However, these prior art valves do not provide for the inflation of the inflatable means on the valve disc in the inoperative position of the disc to prevent fluid leakage about the point where the valve operator passes through the housing of the valve.